The technique of broadcasting using DASH (dynamic adaptive streaming over HTTP (hypertext transfer protocol)) technology is one of the existing technologies that enable that broadcasting of multimedia contents on a communications network.
By way of an illustration of these technologies, FIGS. 1a and 1b present a known configuration where a DASH client is embedded in a user terminal 100, for example a mobile terminal connected to an access node 140 of a mobile network, for example a base station of a 2G, 3G, 4G or other type of cell network.
At a step E101, the user terminal 100 identifies itself with an identification server 110 of a multimedia content provider. If the terminal 100 is not known, it can also be a step of registration with this content provider.
At a step E102, the identification server 110 gives the user terminal 100 confirmation of its successful identification or, as the case may be, confirmation of its registration.
To this end, the exchanges between entities can transit through different servers included in the network core 150, for example an SGW (Serving Gateway) or PGW (Packet Data Network Gateway).
At a step E103, the user terminal 100 sends a DASH request to a managing server 120 of the multimedia contents provider. More specifically, this request relates to a multimedia description file or manifest file called an MPD (media presentation description), corresponding to a particular multimedia content that the user of the user terminal 100 is seeking (whether it is to download it and subsequently use it or else to immediately use in streaming mode).
Indeed, the DASH technology stipulates that a given multimedia content, for example a video or sound content, is available in the form of segments, called chunks, each corresponding to a certain duration of the multimedia content in question. Different chunks can correspond to a same fraction of the multimedia content, i.e. to a same passage of the video or sound content in question, but each with a different quality, each corresponding to a different encoding bit rate, for example because of a different resolution or a different encoding system.
At a step E104, the MPD manifest file corresponding to the multimedia content sought is returned to the user terminal 100.
The DASH client installed in the user terminal 100 then interprets the MPD file received and selects chunks of the desired multimedia content that present a quality and hence ultimately a bit rate that matches its need (for example the size and resolution of the screen of the terminal if it is a video content).
At a step E105, the user terminal 100 sends another request for obtaining the pre-selected chunks to a multimedia contents server 130 belonging to a content delivery network (CDN) of the multimedia content provider. This provider then returns the requested chunk or chunks at a step E106, this chunk or chunks corresponding to the quality and therefore to the bit rate selected by the DASH client installed in the user terminal 100.
Thus, in the existing approach, the DASH clients interpret MPD files representing the content of provider files of servers of multimedia contents providers and dynamically select the quality and therefore the bit rate most favorable to their own needs, i.e. without taking account of the needs of other users. This behavior which raises no particular problem in wired applications where each user has a distinct transmission channel, becomes a source of problems in a cell radiocommunications system in which several users connected to a same network cell share only one radio resource, this radio resource being finite. This behavior can effectively lead to an unfair distribution of the bandwidth available for the different users connected to a same network cell, especially when there is congestion in this network cell.
In addition, DASH clients often make an inaccurate assessment of network bandwidth. The decision made by DASH clients in selecting the quality and associated bit rate is therefore often sub-optimal, leading to a deterioration of the overall quality experienced by the users on the whole.
This set of problems and issues is aggravated in modern cell technology such as 4G technology, for which the user applications are increasingly multimedia-oriented and for which the quantity of data transferred is increasingly large.
Besides, there are major fluctuations in network bandwidth in a radiocommunications network cell related to changing conditions of propagation. This also contributes to the difficult of estimating the network bandwidth for such applications.
However, the cell network MEC (Mobile Edge Computing) technology which is being standardized with the ETSI (European Telecommunications Standards Institute) offers the advantage of making use of a location on the edge of a cell network to optimize applications dedicated to the users of such a cell network. To this end, MEC technology proposes to introduce dedicated MEC servers. Such MEC servers are implanted in contact with base stations managing the radio part of the cell networks, for example the eNodeB in 4G technology, so as to host dedicated applications and give them both the flexibility of being able to manage traffic to and from mobile users and the possibility of accessing information in real time on the working of the radio part of the network. These applications can be managed either directly by the operator of the network or by third parties, for example contents providers.
It can thus be seen that MEC technology could be adapted to problems of managing bit rates of broadcasting multimedia contents in a cell network and in a multi-user environment.
Certain research work has recently been made on the subject. In particular, the method described in the article by J. Fajardo, I. Taboada, and F. Liberal, «Improving content delivery efficiency through multi-layer mobile edge adaptation,» Network, IEEE, vol. 29, no. 6, pp. 40-46, November 2015, proposes an assisted mobile network approach based on a continuously adaptive HTTP protocol with a multilayer encoding and MEC tools. In particular, a Mobile Edge-DASH adapting function situated within the cloud radio access network or centralized radio access network (C-RAN) is being introduced to combine the network context, the user context and the state of the cell. However, this approach does not resolve the issues and problems described here above related to the behavior of DASH clients which select the quality of the proposed chunks in the MPD files solely on the basis of their own needs and capacities.
More generally, there is as yet no mechanism to maximize the quality of the overall experience of DASH clients situated in a same radiocommunications network cell.
There is thus a need to improve the user experience during simultaneous access to multimedia contents available on remote servers by terminals sharing a same limited radiofrequency network of a cell radiofrequency network type, especially in avoiding network congestion.
There is also a need that the sharing of radiofrequency resources among the different users should adapt in real time to the operational conditions of the network cell.